Interpretive Summary: Puroindoline genes were discovered and cloned almost two decades ago. Their main function was identified with the regulation of grain texture, even though they are associated with processing quality and plant resistance in some reports. Unlike puroindoline a and b, with a relatively clear function of mainly modulating grain texture in bread wheat, puroindoline b-2 was found only recently with the report of Wilkinson et al. (2008). The main function Puroindoline b-2 is still not clear, even though in a previous study we reported that the Puroindoline b-B2 gene may have a larger impact on soft wheat cultivars than hard, and that the Pinb-B2v3 allele was associated with preferable grain yield traits compared to the Pinb-B2v2 allele in bread wheat. In this study, we further analyzed the association of Pinb-B2v3 allelic variation with kernel hardness, yield-related traits and flag leaf size, and found that wheat cultivars with Pinb-B2v3b possessed preferable yield-related traits while wheat cultivars with Pinb-B2v3a possessed relatively larger flag leaf size. It will benefit for maker assisted selection during the improvement of grain yield of bread wheat.

Technical Abstract:
In a previous study, we reported the association of Puroindoline b-B2 variants with grain texture, yield-related traits and flag leaf size in bread wheat (Triticum aestivum L.) and found that cultivars with Pinb-B2v3 possessed relatively preferable yield-related traits. In this report, we further identify the allelic variation of Pinb-B2v3 variant that could be divided into three different alleles of Pinb-B2v3a, Pinb-B2v3b and Pinb-B2v3c. Pinb-B2v3a and Pinb-B2v3c share the same deduced amino acid sequence. The result of Chi-square test showed that heredity of puroindoline b-2 variants was independent in bread and durum wheat. Further analyzing the association of Pinb-B2v with kernel hardness, yield-related traits and flag leaf size indicated that cultivars with Pinb-B2v3b possessed relatively higher SKCS hardness index in soft wheat and higher thousand-kernel weight, kernel diameter, grain number per spike, grain weight per spike and grain weight per plant than those of Pinb-B2v2, Pinb-B2v3a and Pinb-B2v3c in the bread wheat cultivars surveyed, Cultivars with Pinb-B2v3a possessed relatively greater flag leaf width, length and area among four Pinb-B2v alleles. d-CAPS (Derived Cleaved Amplified Polymorphic Sequences) markers were developed for identification of Pinb-B2v3b and Pinb-B2v3c alleles and will be useful for screening early generation materials by MAS (marker assisted selection) during wheat breeding. The results of quantitative real-time PCR indicated that relative expression level of Pinb-B2v3b was significantly higher than those of Pinb-B2v2, Pinb-B2v3a and Pinb-B2v3c, possibly suggesting that expression level of Pinb-B2v3 was positively correlated with preferable yield-related traits. This study could provide useful information for the improvement of wheat yield and better understanding the molecular and genetic basis of wheat grain yield.